A metabolic pathway is a series of_______reactions, often located in a specific part of the cell.

enzyme-catalyzed

Without enzymes,

reactions would be too slow for cells to survive

Enzymes provide a way to couple energetically ___________reactions with______.

-unfavorable

-favorable reactions

Catabolic reactions go through_________where it takes electrons and breaks bonds

degradation

Degradation breaks_______to_________

-complex metabolites

-simple products

Anabolism reactions go through______where_______ turn to _______

-biosynthesis

-simple products

-complex metabolites

What macromolecules are broken down in catabolism?

proteins, polysaccharides, triglycerols

The end goal of catabolism

CO₂

_____is the electron carrier produced by glycolysis

NADH

Catabolism is____, and anabolism is____

oxidative, reductive

When the energy state of the cell is LOW, we would expect to see reactions taking place with end product such as?

CO₂

If, in the course of a reaction, NAD⁺ goes to NADH, then the reaction is____

oxidative

Metabolic pathways are localized within different cellular compartments

Compartmentalization

What mechanisms occur in the cytosol?

glycolysis, PPP, fatty acid biosynthesis, many GNG reactions

What mechanisms occur in the mitochondrion?

Citric acid cycle, oxidative phosphorylation, fatty acid oxidation, amino acid breakdown, and electron transport

What are the four strategies to control enzymes?

-allosteric control

-covalent modification

-substrate cycles

-genetic control

Allosteric control includes substrates, products, and coenzymes of the pathway. This is ______feedback regulation

negative

covalent modification is a

global response

Enzymes that control flux of a pathway have specific sites that can be _______

covalently modified

Covalent modifications are_______ such as hormones

controlled by signals

In substrate cycles, the foward reaction is________while the reverse reaction is______

- accelerated

-slowed down

In genetic control, altering the concentration of enzymes can lead to

altering enzyme activity

ATP-->(ADP+Pi) doesn't have the highest free energy because

it needs time to replenish

ATP--->(ADP+Pi) has a free energy charge of_____ and needs______to make more ATP.

• -30.5 kJ/mol
• +30.5 kJ/mol

Hydrolysis increases _____ and _______

-resonance stabilization

-energy of solvation

Hydrolysis decreased_____

-electrostatic interaction

-Phosphoenolpyruvate, 1,3-bisphosphoglycerate, phosphocreatine transfer to make ATP

- ATP helps in the production of Glucose-6-phosphate and glycerol-3-phosphate

NAD⁺ and FAD _____electrons

accept

Reduction___electrons

gain

Oxidation___electrons

loses

Electron transfer can be

-directly as e^-

-As H⁺ atom: 1e^- transferred

-As hydride ion (H^-): 2e^- transferred

NADH is a common electron carrier and always transfers_____

two e^-at a time

what does biosynthesis rely on?

reducing equivalents from NADH

What structure is this?

flavin(FAD)

reduced: FADH₂

oxidized: FAD

Mg²⁺interacts with the negative charges on the phosphate group to shield negative charges,

making the molecule more stable

Pentose phosphate pathway is an alternative pathway that allows for____production and provides biosynthetic precursors

NADH

GNG is a pathway in the _____and_____ that allows for biosynthesis of glucose from pyruvate, lactate, and amino acids.

-liver

-kidney

Glycolysis and GNG are reciprocally regulated by allosteric effects, _______ and _______

-covalent modification

-changes in enzyme synthesis rates

Low affinity transporter in hepatocytes (liver) and pancreatic cells

GLUT2

Higher affinity transporter in adipose tissue and muscle cells

GLUT4

Is driven by concentration and hormones, independent of Na⁺

GLUT1-4

GLUT2 has about a Km=15mM and captures excess glucose primary for

Storage

GLUT2 is considered to be first order kinetics because______.

-transport is directly dependent on glucose concentration

low affinity=

fast chemistry

GLUT4 has about a Km=5mM which means transport is saturated with slightly

high blood glucose levels

GLUT4 is considered to be

zeroth order of kinetics because its constant rate.

After a meal, glucose is____.

Before a meal, glucose is______

-very high

-very low

high affinity=

slow chemistry

A stimulated cell of insulin causes for localization of _______to plasma to boost glucose uptake in cell

glucose receptors

Glycolysis occurs in the____ and doesn't require

-cytoplasm

-oxygen

The products of glycolysis are

ATP, pyruvate, NADH

The three fates of pyruvate are

-TCA cycle, Lactic acid fermentation(muscles), alcohol fermentation in yeast

Investing ATP allows for glucose uptake to be____.

Utilizing ATP to irreversibly convert glucose to G6P allows for____

-controlled

-the regulation uptake in glucose

G6P is not allowed to cross the plasma membrane due to____

phosphorylation

What sugars can hexokinase be used for?

-glucose

-fructose

-mannose

Hexokinase has high affinity, and provides_____

direct feedback regulation by G6P.

The liver stores extra___ and doesn't compete with other tissues

glucose

What sugars can glucokinase be used for?

glucose only!!

Due to the poor affinity of glucokinase, it allows for the liver

to get what is left over

Glucokinase has a

different regulatory mechanism

What substrate is the branch point for several metabolic pathways?

G6P

How does hexokinase and glucokinase prevent ATP from reacting with water?

glucose binding (conformational change that orients glucose and ATP and excludes water)

What intermediate is formed when making G6P to F6P?

enediol intermediate

In phosphofructokinase, a decrease in ATP and an increase in AMP causes for

PFK to respond to cells energy demands and turn glycolysis on and off.

The R-state(high affinity) of PFK allows for the _____

stabilization of AMP

The T-state(low-affinity) of PFK allows for the_____

stabilization of ATP

Positive allosteric effectors shift equilibrium to favor

r-state

Negative allosteric effectors shift equilibrium to favor

t-state

PFK is first

committed step in glycolysis

PFK activity_____ when the energy status of cell is low, and _____-when the energy status is high.

-increases

-decreases

Is PFK tightly regulated?

YES

F-2,6-BP stimulates PFK by decreasing

inhibitory effects of ATP

In aldolase, each end is phosphorylated before

cleaving because its trapped

What does the aldolase enzyme found in animal tissues form into?

-covalent Schiff base E-S intermediate

What does the aldolase enzyme found in bacterial and fungi form into?

-doesn't form E-S intermediate but contains a Zn²⁺to help shield the oxyanion intermediate

Which carbon in glucose becomes C=O in DHAP after both aldolase and triose P isomerase?

C#2 or C#5

TPI is a near perfect enzyme because it has

high affinity/fast chemistry

In glycolysis first phase, ___ATPs are consumed. In the second phase,____ATPs are produced. Which results in a net ATP yield of __ATPs per glucose.

-2, 4, 2

Glyceraldehyde 3-phosphate dehydrogenase uses_______ as a cosubstrate which involves the exchange of electrons.

NAD⁺

Gly-3P is oxidized to

1,3-BPG

Phosphoglycerate kinase transfers a phosphoryl group from 1,3-bisphosphoglycerate to ADP to ATP

substrate-level phosphorylation

A___is an enzyme that catalyzes the migration of a function group within the substrate molecule

mutase

The enolase reaction in glycolysis is a

dehydration reaction, not a redox reaction

Pyruvate Kinase irreversible in vivo

.

ATP production via glycolysis doesn't require____

oxygen

What are the key regulatory steps (irreversible)?

-hexokinase/glucokinase

-phosphofructokinase

-pyruvate kinase

Flexible loop closes over TIM active site and creates

Methylglyoxal formation

What other substrates can be used for glycolysis?

fructose, galactose, and mannose

Fructose (muscle) requires____

hexokinase

A tagged glucose (UDP) must occur to

enter glycolysis

What enzymes are needed for galactose to go through glycolysis?

galactokinase, galactose-1-phosphate uridylyl transferase, UDP-galactose-4-epimerase, phosphoglucomutase

What enzymes are needed for mannose to go through glycolysis?

hexokinase and phosphomannose isomerase

What enzyme is needed for fructose to go through glycolysis in the muscle?

hexokinase

What enzymes are needed for fructose to go through glycolysis in the liver?

-fructokinase

-fructose-1-phosphate aldolase,

-glyceraldehyde kinase,

-alcohol dehydrogenase

-glycerol kinase,

-glycerol phosphate dehydrogenase,

-triose phosphate isomerase

Activators:

AMP, F16BP (more pyruvate, more ATP)

Inhibitors:

ATP(stabilize t-state), Acetyl-CoA (less pyruvate), and Alanine (carbon skeleton)

Important regulation steps in glycolysis in liver

1. glucokinase

2. PFK

3. Pyruvate kinase

Fructose only metabolizes in excess amounts by_____ and excess sugar become____

-the liver

-fat

Glycerol is produced in the decomposition of____.

-triacylglycerols

In the ethanol endpoint of glycolysis, is a 2 step process catalyzed by

-pyruvate decarboxylase

-alcohol dehydrogenase

In the lactate endpoint of glycolysis, pyruvate is reduced by _____ and is reversible

lactate dehydrogenase (larger amounts of ATP generated)

Aerobic glycolysis generates more ATP but has a ______

much slower rate

Anaerobic glycolysis generates less ATP but has a

much faster rate

What is the Cori cycle?

liver and muscle work together to keep sprinting

What type of twitch muscles do these characteristic represent?

-dark in color

-has endurance

-is aerobic

slow twitch

What type of twitch muscles do these characteristic represent?

-is anaerobic

-light in color

-fatigues easily

fast-twitch

Humans do not have_____, but they do have_____

-PDC

-ADH

Humans do not have pyruvate carboxylase, but they do use______

thiamine pyrophosphate(TPP)

Does TPP allow for a better reaction pathway?

YES

..

Mechanism of pyruvate decarboxylase

look at the mechanism

The body has enough glucose to supply for one day, so it must be made from

non-carbohydrate precursors

The brain functions on glucose and accounts for 75% of

daily consumption of glucose

Muscles also require______

glycolysis

GNG meets the body's glucose needs under_____

fasting conditions

Our brains cease to function when blood glucose concentration is_____

<2.5 mM.

Humans consume about___per day

160 g

The reactions that goes from pyruvate to TCA, occur in the

mitochondria

Body fluids contain only ___ of glucose.

Glycogen stores yield____of glucose.

-20g

-180-200g

What are the substrates for GNG?

pyruvate, lactate, glycerol, amino acids and all TCA intermediates

Acetyl-CoA cannot provide for

net synthesis of sugars

GNG has four different enzymes from glycolysis because

the conversion of Pyruvate to PEP requires two steps

Acetyl CoA is a main carbon source for TCA cycle where an increase in acetyl-coA means

cell has plenty of "fuel"

Biotin is a vitamin that serves as a

mobile CO₂ carrier

Pyruvate carboxylase uses ATP to load CO₂ onto ____then delivers it to ______

-biotin

-pyruvate

PEP carboxykinase uses

GTP rather than ATP

Why does cell add CO₂ with pyruvate carboxylase and then take it back off with PEPCK?

decarboxylation drives the formation of the enol that GTP phosphorylates

Fructose-1,6-bisphosphatase allosteric regulation:

-citrate simulates(makes glucose)

-fructose-2,6-bisphosphate inhibits(activates PFK (glycolysis on))

-AMP inhibits (low energy)

F1,6BPase: What gets inhibited vs. activated?

-AMP inhibit (GNG off)

+ATP(allosteric site)

+Citrate (allosteric site)

-F2,6P(turns GNG off)

PFK1: What gets inhibited vs. activated?

+AMP(low energy)

-ATP (allosteric sites)(high energy)

-citrate(allosteric site)(high energy)

+F2,6P(turns GNG on)

PFK-2 domain

production

F2,6BPase domain

breakdown

the presence of G-6-Pase in ER of the ____and______ cells makes GNG possible

-kidney

-liver

Muscles and brains DO NOT do______

GNG

Glucose-6-phosphatase reaction involves_____by a histidine nitrogen and formation of a_________

-nucleophilic attack

- phosphohistidine intermediate

Vigorous exercise lead to the build up of__________due to O₂ shortage and the need for more glycolysis

lactate and NADH

NADH is reoxidized during the reduction of

pyruvate to lactate

Lactate is then reduced to the liver where it can be reoxidized to

pyruvate by liver LDH

GNG is driven by the consumption of___-

6 nucleosides triphosphates

When glycolysis is turned on, GNG should be

turned off

When cell's energy status is high, glycolysis should be off and should be used for

synthesis and storage of glucose

When cells energy status is low, glucose should be rapidly

degraded to provide energy(needs ATP)

An individual is sprinting, what type of regulation is going on in terms of glycolysis and GNG?

IN THE MUSCLE

-glycolysis is on, production of ATP is critical, so anaerobic glycolysis is occurring

-ATP is being generated as quickly as possible

An individual is sprinting, what type of regulation is going on in terms of glycolysis and GNG?

IN THE LIVER

-GNG is on, production of NADH and glucose for use in muscles is critical

Pentose phosphate pathway has 2 phases:

oxidative phase and nonoxidative phase

The oxidative phase of PPP uses glucose metabolism to

help supply NADH for reductive reactions

The nonoxidative phase of PPP uses glucose metabolism to supply

ribose-5-phosphate

The first 4 substrates makes

2NADPH G6P--->5C sugar-P

The bottom substrates interconvert

3C,4C,5C,6C,7C sugars

NADH is mainly in______form and removes 2e^- during fuel metabolism

oxidized

NADPH is mainly in _______form and adds 2e^- during biosynthesis and detox of free radicals

reduced

PPP operates mostly in

cytoplasm of liver and adipose cells(fat)

G6P dehydrogenase is regulated by NADPH levels

-NADPH is a _____, cytosolic levels of NADP⁺/NADPH dictate enzymes activity

inhibitor

oxidation of an aldehyde

Hyrdolysis of lactone occurs both

enzymatically and non-enzymatically

6-phosphoglucono8-lactone is hydrolytically unstable, so it readily undergoes

spontaneous ring opening hydrolysis

reaction 2: gluconolatonase accelerates the spont. ring opening hydrolysis in order to

prevent the accumulation of 6-phosphogluconolactone which is toxic

The 2 phases of oxidative decarboxylation:

1. NADP⁺ dependent dehydrogenation yielding a beta-keto acid
2. decarboxylation event that produces ribulose-5-phosphate

Phosphopentose isomerase has an

enediol intermediate

Ribose-5-phosphate is used in biosynthesis of

coenzymes, nucleotides, and nucleic acids

Phosphopentose Epimerase change in position of acidic proton and has a

enediolate intermediate

Transketolase is the transfer of _____ from ketose(donor) to aldose(acceptor) and utilizes _____

-2-C

-TPP

Although reaction is called transketolase, the group that is transferred is a_____

aldol

Transaldolase converts ___skeleton to a useful______skeleton, and it transfers_____

• 7-C
• 6-C
• 3-C

The transaldolase mechanism involves attack on the substrate by

an active-site lysine

The nonoxidative steps consists of

-phosphopentose isomerase

-phosphopentose epimerase

-transketolase (TPP-dependent)

-transaldolase (Schiff base mechanism)

What does phosphopentose isomerase do?

coverts ketose to aldose

What does phosphopentose epimerase do?

epimerizes at C-3

What does transketolase(TPP-dependent) do?

transfer of two-carbon units

What does transaldolase do?

transfers a 3 carbon unit

What are the 5 variations of PPP?

1. both ribose-5-P and NADPH are needed
2. more ribose-5P than NADPH is needed
3. More NADPH than ribose-5-p is needed
4. NADPH and ATP are needed, but ribose-5-p is not

1) More ribose-5-P than NADPH is needed

What types of situations would call for this?

rapidly dividing cells that are synthesizing DNA

3) more NADPH than ribose-5-P is needed:

when fatty acids are being synthesized,

NADPH is consumed rapidly

4) NADPH and ATP are needed, but ribose-5-P is not

Generate intermediates for glycolysis,

producing pyruvate that can go through TCA

More than likely the goal will be_____ in PPP

ribose-5-phosphotate

Is a multi-branched polysaccharide of glucose

glycogen

What is glycogen used for?

-degraded when glucose is needed

-it is synthesized for energy

Glycogen is the readily mobilized storage form of_____

glucose

The liver has higher concentrations of glycogen stored due to controlling

blood and glucose levels (must react quickly to glucose and blood changes)

______is where most of the glycogen is stored

Muscle

The muscle consists of_____glycogen, triggers fight or flight, and quickly mobilized

1-2%

The liver is up to______glycogen.

10%

the liver must maintain about ______blood glucose.

The liver also has a 12 hour supply of_____

-5mM

-glucose

Glycogen has_____and linkages

alpha(1->6) and alpha(1->4)

Amylase is a saliva enzyme that hydrolysis the alpha(1->4) glycosidic bond of_____

starch

An enzyme that hydrolysis one glucose residue at a time and is capable of alpha(1->6) glycosidic bonds and leaves glycogen with one less point

alpha(1->6) glucosidase

An enzyme that transfers trisaccharide unit and converts it to a alpha(1->4) bond

Oligo(alpha(1->4), alpha(1->6))glucanotransferase

α-amylase is found in_____ and β-amylase is found in____

-animals

-plants

Endoglycosidase hydrolysis α(1->4) linkages which produces a

mixture of limit dextrin

Starch digestion is highly efficient and almost 100% of digested food is____ and ____-

-absorbed

-metabolized

How is degradation achieved?

by a heavily regulated enzyme (glycogen phosphorylase)

Glycogen degradation in muscles and liver indicate important energy reservoirs stored in the

-cytosol

Allows for the breakdown of glycogen into glucose1-P

glycogen phosphorylase

Glycogen phosphorylase is activated by:

-Allosteric control (local control)

-covalent modification(global control)

Glycogen phosphorylase:

ATP and glucose-6-phosphate is a________

feedback inhibitor

Glycogen phosphorylase:

The response to the concentration of the substrate_____-

-(Pi)

Glycogen phosphorylase:

____is a positive effector that binds at the same site as ATP

AMP

T-state is stabilized by____ and ________.

(high ATP signals no need for energy)

ATP and G6P

R-state: stabilized by______.

(low ATP signals a need for energy)

AMP

The breakdown of a molecule directly using phosphate

Phosphorolysis

What type of reaction is this?

Isomerization because a phosphate group is being relocated from C1 to C6

Glucose units are activated for transfer by formation of sugar nucleotides

Glycogen synthesis-I

What are other examples of activation?

aminoacyl-AMP, Fatty acyl-AMP, etc.

Glycogenin is a protein that

forms the core of a glycogen particle

In glycogen synthase, what gets kicked off?

the tag (UDP)

Glycogen synthase is allosterically regulated by:

increase in G6P, when G6P is high,

ATP levels are high, and AMP is low

Glycogen synthase is less active in the______form and more active in the______form

-phosphorylated

-dephosphorylated

90% of glycogen cleaved into G1P which is

isomerized into glucose-6-phosphate

10% are the branched residues that are hydrolyzed into glucose can than be

phosphorylated into G6P

The complete oxidation of G6Pvia glycolysis, TCA cycle and oxidative phosphorylation yields 38 molecules of ATP which means its effciency of storage is

97%

what are the 3 fates of G6P?

-glycolysis

-conversion to free glucose into blood stream (liver)

Glucose-1-phosphate cannot escape the cell because

it allows cell time to determine needed conversion

Why galactose and glycogen metabolism involve UDP?

UDP: conenzyme-like carrier of hexose groups

If O₂ levels are reestablished in the muscle,

lactate can be converted to pyruvate

What are the three important hormones?

1. insulin
2. glycagon
3. epinephrine

What is the allosteric regulation for glycogen synthase?

G6P(makes glycogen)

What is the allosteric regulation for glycogen phosphorylase?

ATP (breakdown glycogen)

If there is excess sugar and energy, there is an increase in G6P, ATP, and a decrease in AMP. This result in

making glycogen

If there is low sugar but a energy demand, there is a decrease of G6P, ATP, and an increase in AMP. This cause the

breakdown of glycogen

Insulin (high blood sugar) cAMP________ and stores glycogen and fat

decreases

Epinephrine(adrenalin)_______cAMP and give fight or flight signals as well as mobilizing glycogen

increases

Glucagon(low blood sugar) cAMP is ______ in the ______, and it mobilizes liver glycogen and sends glucose to brain

-increased

-liver

Insulin is secreted as a response to

increased glucose levels in blood

Is a peptide hormone produced from beta-cells in the pancreas

Insulin

The body utilizes different pathways that use glucose to

deplete the high concentration of glucose

When lots of glucose is about to be needed, what can aid in producing it?

epinephrine

Where is glucagon released from?

α-cells in the pancreas and travels to liver

Where is epinephrine released from?

adrenal gland

Glucagon and epinephrine inhibit glycogen synthase and activate

glucogen phosphorylase

The end goal of hormone -activated enzymatic cascade has an end goal of

activation of glycogen phosphorylase

What structure is this?

cAMP

Epinephrine activates glycogen_____ and inhibits glycogen_______.

-breakdown

-synthesis

Glucogen stimulates liver to release glucose from

glycogen stores into the blood stream

Exercise--> low blood glucose->

high cAMP

exercise requires lots of

ATP

Glucagon specifically targets the

liver

Low blood sugar-->glucagon secreted by pancreas-->

cAMP levels increase in liver

Liver's response to LBG:

1. LBG
2. Increased glucagon secreation
3. increased cAMP
4. increased enzyme phosphorylation
5. ?
6. ?
7. ?
8. ?

5. Activation of FBPase-2 and inactivation of PFK-2

6. Decreased F2,6P

7. inhibition of PFK and activation of FBpase

8. Increased GNG

Excess food+ no exercise-->

high blood glucose

Some glucose will be retained as glycogen but only 1-2% is stored, the rest must be dealt by the

liver